This invention relates to processing machines for sheet material, e.g., machines for die cutting paperboard boxes out of paperboard sheets. In the past, such machines have included a plurality of grippers for gripping an edge of a paperboard sheet and means for moving the grippers to draw the paperboard sheet along a predetermined path for die cutting and printing. The grippers are attached to a rigid bar which is connected between a pair of endless chains which move the bar along the predetermined path. A plurality of such gripper bars are spaced apart along the chains. The endless chains are driven intermittently to move the paperboard sheets from one work station to another and then to pause while operations are performed on the sheets at each work station.
At one station in such prior art machines the paperboard sheet is die cut into the desired form, with uncut portions being left in the leading edge of the die cut form to keep it attached to the leading waste edge gripped by the grippers. The uncut portions enable the grippers to continue carrying the die cut form along the processing path. At the last work station in the path, the grippers are opened to release the leading waste edge and die cut form, which drop onto a conveyor which carries them out of the machine. The leading waste edge is then manually stripped from the individual die cut forms and the forms are then manually stacked for packaging.
The above-described prior art machine is automatic in all features except for the removal of the leading waste edge from the cut form. Paperboard sheets are fed into the machine automatically from a stack of sheets and are processed automatically at all work stations in the machine. But the product which leaves the machine is not finished and requires manual removal of the leading waste edge by which the die cut form is carried through the machine. Thus the machine's speed is severely limited by the necessity of hand operation on each individual product, which also substantially raises the cost of the process.